Who was the man that wrote a letter to Truman expressing his concerns of the iron curtain?

This man would be Winston Churchill. Winston Churchill was a staunch anti-Communist who feared that Communism might engulf all of Europe. The Iron Curtain he is referring to is the Soviet's control of Eastern European countries. These countries, called satellite nations, acted as a buffer between Western Europe and Russia.

Winston Churchill was the man that wrote the letter to Truman